Physiology concepts standard

Physiology

• The study of how living organisms function
• Focuses on the functions of the body systems and how these systems interact

Specialties of Physiology

• Cell physiology: focuses on the functions of individual cells
• Special physiology: explores the functions of specific organs
• Pathophysiology: studies the physiological changes that occur during disease

Principal Life Processes

• Responsiveness: the ability to detect and respond to changes in the environment
• Movement: includes the motion of the whole body, individual organs, single cells, and even organelles inside cells.
• Growth: an increase in size and complexity, due to an increase in the number of cells
• Differentiation: the process by which unspecialized cells become specialized into particular types of cells.
• Reproduction: the formation of new cells or new organisms
• Metabolism: all chemical reactions taking place in the body

Levels of Physiological Organization

• Chemical/molecular level: atoms combine to form molecules
• Cellular level: molecules form organelles
• Tissue level: similar cells that work together to perform a specific function
• Organ level: two or more tissues that work together
• Organ System level: a group of organs that work together to perform a common function
• Organism level: all the organ systems of the body working cooperatively

Homeostasis

• Maintenance of a relatively stable internal environment
• Essential for cell survival and proper function
• Examples: regulating body temperature, blood pressure, and blood glucose levels

Regulatory Mechanisms

• Intrinsic regulation: occurs within a specific organ
• Extrinsic regulation: results from the activities of the nervous or endocrine systems that control or adjust the activities of many systems simultaneously

Feedback Loops

• Control mechanisms that help maintain homeostasis
• Components:
  • Receptor: detects changes in environment, sending a message to the control center
  • Control center: receives, processes, and integrates information from the receptor
  • Effector: receives commands from the control center and carries out a response
• Negative feedback: reduces the initial change
  • Most important mechanism for maintaining homeostasis, examples: regulation of body temperature, blood pressure, and blood glucose levels
• Positive feedback: exaggerates the initial change
  • Usually used for short-term processes, examples: childbirth, blood clotting, and the generation of nerve impulses

Communication and Integration

• Homeostasis relies on chemical (hormones) and electrical (nerve impulses) signals
• Communication essential for survival and function

Cell-to-Cell Communication

• Direct cytoplasmic transfer: occurs between cells that are connected by gap junctions
• Local chemical communication: occurs between cells that are close to each other
• Long-distance communication: occurs between cells that are far apart
  • Involves the use of hormones, neurotransmitters, neurohormones

Components of Cells

• Plasma membrane: the outer boundary of the cell
  • Fluid mosaic model: membrane consists of a phospholipid bilayer with embedded proteins
• Cytosol: the fluid inside the cell
• Organelles: specialized structures within the cell
  • Inclusions: non-living substances that may be present in the cytoplasm, examples: glycogen granules, lipid droplets, and pigment granules

Plasma Membrane

• Functions:
  • Physical isolation: separates the cell’s internal environment from the external environment
  • Regulation of exchange with the environment: controls the movement of substances into and out of the cell
  • Sensitivity to the environment: receives signals from the environment
  • Structural support: helps maintain the shape of the cell
• Types of membrane proteins:
  • Integral proteins: embedded in the phospholipid bilayer, many act as channels, receptors, carriers, or enzymes
  • Peripheral proteins: bound to the inner or outer surface of the membrane

Membrane Transport

• Passive transport: does not require energy
  • Types:
    • Diffusion: movement of a substance from an area of high concentration to an area of low concentration
    • Osmosis: diffusion of water across a selectively permeable membrane
• Active transport: requires energy (ATP)
  • Types:
    • Carrier mediated transport: substances bind to membrane proteins, and the proteins facilitate their movement across the membrane
    • Vesicular transport: substances are transported in membrane-bound vesicles

Diffusion

• Characteristics:
  • Movement from a region of high concentration to a region of low concentration
  • Movement down the concentration gradient
  • Depends on the size of the particles
  • Requires no energy input
  • Important for the movement of oxygen, carbon dioxide, nutrients, and waste products

Osmosis

• Characteristics:
  • Movement of water molecules across a selectively permeable membrane
  • Movement from an area of high water concentration to an area of low water concentration
  • Will move towards the solution which has the higher concentration of solutes
  • Influenced by the solute concentration
  • Important for maintaining cell volume and fluid balance

Electrical Impulses

• Cells that use electrical impulses are excitable cells
  • Types: neurons and muscle cells
• Electrical impulses generated by changes in the distribution of ions across the cell membrane
• Key ions: potassium (K+) and sodium (Na+)

Membrane Potential

• Resting potential: the potential difference across the cell membrane when the cell is at rest
  • Typically around -70 mV
• Depolarization: a shift in the membrane potential towards 0 mV
  • Can be caused by the opening of sodium channels
• Repolarization: a return of the membrane potential to the resting potential
  • Caused by the closing of sodium channels and the opening of potassium channels
• Hyperpolarization: a shift in the membrane potential below the resting potential
  • Caused by the continued opening of potassium channels
• Equilibrium potential: the membrane potential at which the electrical gradient is equal and opposite to the chemical gradient
  • The movement of ions across the membrane stops
  • For example, the equilibrium potential for sodium (Na+) is +60 mV

Ion Channels

• Types:
  • Voltage-gated: open in response to changes in membrane potential
  • Ligand-gated: open in response to the binding of a ligand to the channel protein, examples: neurotransmitters, hormones
  • Mechanically-gated: open in response to a mechanical stimulus
• States:
  • Closed: not allowing ions to pass through
  • Open: allowing ions to pass through
  • Inactivated: closed and incapable of opening

Graded Potentials

• Local changes in membrane potential
  • Can be depolarizing or hyperpolarizing
  • The change in membrane potential is proportional to the strength of the stimulus
  • Decrease in intensity with distance from the site of the stimulus

Action Potentials

• Brief, stereotyped (all-or-none) changes in membrane potential
  • Occur when the membrane potential reaches a threshold value
  • The amplitude of the action potential is always the same
  • The duration of the action potential is also always the same
  • Important for the transmission of nerve impulses and muscle contractions

Steps Involved in Generating an Action Potential

• Resting potential: the neuron is polarized, with a negative charge inside the cell and a positive charge outside the cell
• Depolarization: the membrane potential becomes less negative, due to the opening of sodium channels
• Repolarization: the membrane potential becomes more negative, due to the closing of sodium channels and the opening of potassium channels
• Hyperpolarization: the membrane potential becomes more negative than the resting potential, due to the continued opening of potassium channels
• Return to resting potential: the membrane potential returns to the resting potential

Test your knowledge on the essential aspects of physiology, focusing on how living organisms function and the various specialties within the field. Explore key life processes such as responsiveness, movement, growth, and more. Ideal for students studying basic human physiology.